When machining a ceramic block having preformed connection geometry, as disclosed, for example, in EP 1 023 876 A2, the position and orientation of said geometry relative to the geometry of the processing machine must be known. However, the connection geometry itself cannot always be directly surveyed, since an optical surveying device is not always present.
For this reason, ceramic blocks having preformed connection geometry have either not been processed mechanically, or the shape to be machined has not required, for reasons of symmetry, any precise knowledge of the position and shape of the preformed geometry.
In the field of fabricating dental fitted shells from blanks in the form of ceramic blocks, EP 0 160 797 A1 discloses a method of causing the processing tool to contact a specially calibrated area of a holding means for the blank and thus of utilizing the processing tool for locating the position of the center axis of the blank with reference to the processing tool. Preferably, the holding means itself should be shaped such that it is automatically accurately positioned in the processing machine by means of reference stops.
A drawback of this is that it is not possible to precisely locate the position of the abrasive tools relative to the blank, as is necessary for machining blanks having a preformed connection geometry.
The object of the invention consists in making it possible to machine ceramic blocks having a preformed connection geometry and to mechanically fabricate any desired symmetrical or asymmetrical shape from such a block.